Electric heating unit



l.. R. MCCLATCHIE.

ELECTRlC HEATING UNIT. APPLICATION FILED Aue.1.1921.

Patented Oct. 10, 1922,

Inventor. f www@ 5y A/XQLMMQU of the plate grooves With a narrow channel Patented O-ctilO, 1922.

PATENT OFFICE LEWIS ROY MCCLATCHIE, 0F PENETANGUISHEINE, ONTARIO, CANADA.

ELECTRIC HEATING "umm Application lfiled August 1, 19,21.. Serial No. 488,810.

To all 'whom it may concern: Be it lrnown that I, LEWIS Bor Mo- CLAToHIE,a subject of the King of Great Britain, and resident of the town of Penetanguishene, county of Simcoe, Province of Ontario, in the Dominion of Canada, have invented certain new and useful Improvements in Electric Heating Units, described inthe following specification and illustrated in the accompanying drawings, that form part of the same.V ,p

The principal objects of this invention are to devise an electric heating unit which will be extremely simple to manufacture and in which the liznajor portion of the resistance element will be supported above and free from contact with the Walls of the grooves in the porcelainplate.

'A further object is to provide a plate constructinwhich Will ensure a thorough circulation of air around the resistance wire and which will obviate the difficulties met with in the accumulation of dirt in the bottom of the grooves. v

The principal features of the invention consist in the novel formation of the resistance Wire with enlarged coils arranged at intervals to support the intervening coils 'clear of the Walls of the grooves in the insulator plate, and in the novel formation in the bottom whereby the resistance wire is supported with the minimum contact and held centrally inthe grooves of the plate.

A further important feature consists in the novel arrangement of the grooves in the plate to enable the -use of a uniformly distributed three heat element.

In the drawings Figure 1 is a plan view of my improved element.

Figure 2 is a cross sectional view through a portion of the plate.

Figure 3 is a sectional detail taken longitudinally of one of the plate ribs on the line :c of Figure l.

It has been found in practice to be very desirable to support the resistance coil in grooved plates so that the coil does not rest upon the plate for its entire length but this has hitherto been found diflicult and expen; sive to accomplish. l

In the construction herein shown, the resistance coil I is woundin spiral form and et' intervals throughout its length individual coils 2 are enlarged and the greater diameter of the coils 2 supports the intervening groove so that there. will be no coils clear of thev groove in which theelement is placed.

The p ate 3 is formed with the grooves 4 preferably rounded at the bottom 5 and' 60. centrally of the said rounded bottom is formed a smaller longitudinalr groove 6.' When the wire coil is placed in the groove the enlarged coils 2 engage the edges of the smaller groove 6 and the contact is merely 65 at'these points 'Ihis construction also holds the Wire coil centrall within the main contact with the side Walls.

It will be readily seen that with such a construction of groove and coil the contact between the refractory plate andthe live element is reduced to a negligible quantity and further, that by providing the secondary .groove lthere Will be a free air space all around the element which produces the very best results in the maintenance of the device. Further, any particles of dust or dirt falling into the grooves Will not lodge around and foul the lower portions of the element as they will settle in thesmall central groove. f

The arrangement of the grooves 4 and 4 herein shown is peculiar in that two sets of serpentine grooves are internested. 'Ihe 85 groove 4 starting from the terminal 7 has alternate single and double returnl bends which terminate at the opposite side of the plate at the terminal 8. The groove 4 y starting at the terminal 9, which is arranged adjacent to the terminal 7, has alternate double and single return bends which terminate adjacent to the terminal 8.

The two resistance coils thus extend over the complete area of .the plate and they may be so wired that the current may be directed fastener.

lIt Will be understood from this description that the resistance coil will be free to expand and contract without danger lof conf striction as there are no projections of any kind transverse .of the grooves which would restrict their free movement, consequently the life of the Wire Will be greatly lengthened.

W hat ll claim as my invention is l. lin an electric heating unit, a resistance coil havin projections arranged at intervals in its ,length adapted to support the in tervening coils clear of Contact With the supporting insulator.

2. ln an electric heating unit, a resistance coil having coils of enlarged diameter arranged at intervals in its length.

3. ln an electric heating unit, an insula tor plate having the groove for holding the heater coil formed of ltil-shaped cross section, the bottom thereori being depressed centrally to form a shallow secondary groove of lesser diameter than the. main groove, and a heater coil supported on the edges of the secondary groove.

4. lln an electric heating unit, the comloil ,le 1,407

5. ln an electric heating unit, an insulator plate having a pair of internested ser-y pentine grooves, each having alternating single and double return bends, resistance coils in each of said grooves, a terminal connecting one end of each coil, and terminalsl at each oit the other ends of said coils.

LEV/*l5 RY MCCLTCHE. 

